Hydraulic circuits incorporate valves such as pressure relief valves for various reasons, including to protect components, and to ensure the operational safety of the system. There are various valves in the prior art that are used to control the pressure of fluids, which include liquids and gases. One valve uses a sphere or valve ball yieldably biased by a spring or other mechanism against a valve seat to seal the valve and control the, “cracking” or initial opening pressure, and relief pressure. Once the cracking pressure is reached, the valve ball is forced off of the valve seat, and fluid flows through the valve seat. The valve ball moves back onto the valve seat by the biasing mechanism when the pressure is reduced and the relief pressure is reached.
Valves having a valve bore of a cylindrical or frustoconical shape can have undesirable changes in operating pressure at various flow rates, including especially, high flow rates. These valves typically require unduly increased fluid pressure to cause increased valve opening, and this can cause, for example, variation in operating characteristics relative to fluid flow rate.